The thermal transfer process, electrophotographic process, ink jet process, etc. are at present being vigorously investigated as processes relating to formation of color hard copies. Thermal transfer dye-providing processes are more advantageous in many points than other processes since maintainance and operation of the apparatus adapted for the process are simple and the apparatus and expendables therefor are less expensive.
The thermal transfer process involves heating by means of a thermal head a thermal transfer dye-providing material comprising a base film having formed thereon a heat-meltable ink layer to thereby melt said ink and transfer said molten ink to a thermal transfer image-receiving material or heating by means of a thermal head a thermal transfer dye-providing material comprising a base film having formed thereon a colorant layer containing a thermally transferrable dye to thereby allow the dye to migrate and transfer to a thermal transfer image-receiving material. Of the two types, the latter thermal migration transfer type is advantageous particularly for full-color recording with high image quality, because the dye can be transferred to a different layer by changing the energy applied to the thermal head, which facilitates gradation recording.
However, the thermally transferrable dyes for use in the latter type thermal transfer process are required to possess various properties, and extremely few dyes satisfy all of the requirements.
Requirements for the dyes involve, for example, to possess spectral properties favorable for color reproduction, to easily migrate, to be resistant against light and heat, to be resistant against various chemicals, not to undergo reduction in sharpness, not to cause re-transfer of a transfer image, to be easily synthesized, and to facilitate preparation of thermal transfer dye-providing materials. Magenta dyes with spectral properties favorable for color reproduction (particularly a sharp absorption waveform) and excellent light fastness have been desired.
There have been proposed various types of thermal transfer process magenta dyes. For example, anthraquinone series magenta dyes are disclosed in JP-A-60-131293 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"), JP-A-60-159091, JP-A-61-227093 and JP-A-61-262190 and azo series magenta dyes are disclosed in JP-A-60-30391, JP-A-60-30392, JP-A-60-30394, JP-A-61-227091 and JP-A-61-227092. However, these dyes do not have both excellent spectral properties (particularly a sharp absorption waveform) and light fastness.